Nanorobots are machines or robots with a dimensionality at or at least close to the nanoscale. Nanobots would in principle enable complex interactions with and manipulations of other synthesized nanoscale objects. Top-down and bottom-up are used as two different construction paradigms for producing nanoscale materials, devices, and systems. Top-down is what micro/nanoelectronics is all about, and it does it exceptionally well. Bottom-up nanotech approaches, however, use nanoscale components to arrange themselves into increasingly complex assemblies and, ultimately, systems. The promise of a truly bottom-up revolutionary nanotechnology is fun to think about, though, and is the latest rage in the global research community (and popular press). The potential payout to civilization is incalculable. Our ability to synthesize broad new classes of nanomaterials and deploy those in a wide variety of applications is accelerating rapidly.